A tufting machine for forming cut pile fabric conventionally includes a reciprocating needle bar carrying needles which at each machine cycle project a row of loops of yarn through a backing fabric in a direction transverse to the direction of travel of the fabric, loopers which enter and retain the loops, and knives mounted by knife blocks on an oscillating knife bar which cut the loops held on the loopers.
In such a machine it is necessary that all the numerous knife blocks be accurately located on the knife bar at the correct orientation and maintainable in such accurate positioning, notwithstanding the stresses and vibration imposed upon them during operation of the machine.
In an existing machine, each knife block, conveniently carries a pair of upwardly extending knives and has a peg which is received in a hole in the side of the knife bar, the knife block being retained in the desired orientation with respect to the knife block by a clamping screw fitted into a hole in the base of the knife bar to engage the peg. With this arrangement it is difficult to ensure that all the knife blocks are mounted at the correct orientation on the knife bar and it is also difficult to ensure that all the knife blocks will be tightly clamped in position and maintained in their correct correct orientation. Also, the mounting of the knife blocks on the knife bar is a highly skilled operation since the knife blocks must be set individually at the correct angle.